Many types of plastic containers are used for various purposes, such as, for example, storing foods. These include types of containers which can be taken from the refrigerator and placed into a microwave oven. In any such container it is desired to provide an effective seal between the lid and the container itself. It is also desirable to provide an effective seal which can be achieved with the simplest possible structure since this reduces mold and manufacturing costs. Further, the lid should be easy to use, that is, easy to attach to and remove from the container.
Lid to container seals are usually made by providing the upper edge of the container with a protuberance which rides against or fits into a mating part on the lid. The seal is accomplished as the lid is fastened by a pressing or threading action. Many seals are accomplished by merely forcing the lid down over the top edge of the container, but in such arrangements it sometimes is difficult to remove the lid from the container by the prying action required.